The present invention relates to a device for introducing a mobile positioning body of a member onto a tube plate, applicable more particularly to the introduction of mobile positioning bodies intended to successively face all the tubes of the tube bundle of the steam generator of a nuclear power station.
Steam generators comprise a bundle of exchanger tubes, communicating by a tube plate with a water box or compartment, located in the lower part of the generator. The water box is subdivided into a hot part and a cold part, separated by a vertical partition. The installation of moving bodies used for positioning members in front of the holes, whereby said members can e.g. be probes for detecting leaks or faults in the tubes, takes place by human intervention. When it is a self-supporting moving body, the latter is fitted by an operator, who enters the water box and leaves it as soon as fitting has taken place. If it is a supported moving body, e.g. fixed to a rotary arm, it is also necessary for an operator to enter the water box in order to install the rotary arm system.
In both cases, the operator, who has to enter the water box by an opening called a manhole, is exposed to the action of ionizing radiation, whose level is much higher within the water box than outside the manhole. To avoid exposing personnel to such radiation, attempts have been made to use systems permitting the fitting of the moving body without it being necessary for an operator to enter the water box and, if possible, designed in such a way that the operator is outside the envelope hyperboloid of the cones of the trajectories of ionizing rays.
Moreover, in most existing systems, the device remains in place once the moving body has been fixed to the tube plate, which may prevent or disturb the inspection of certain tubes if, for example, the moving body is a probe-carrying body.